The present invention relates generally to the cold-working of workpieces, and, more particularly, to an improved end-working attachment or device for use in a screw machine or a rotary transfer machine, and which is particularly suited for use in rolling threads on a workpiece.
It is known to roll threads on a workpiece. For example, U.S. Pat. No. 3,913,365 discloses a method and machine for rolling threads. Basically, this patent teaches that a plurality (i.e., two or more) of thread-rolling dies may be initially positioned adjacent a workpiece. In the embodiment shown in FIG. 1 of this patent, two dies are provided. However, the embodiment shown in FIG. 10 has threedies. In either event, each die has a cam surface that includes a flattened portion, a first section of gradually-increasing radius, a second section of constant radius, and a third section of gradually-decreasing radius. The dies are interconnected via a gear train. The dies are initially arranged such that the flats thereon are arranged in closely-spaced facing relation to the portion of the workpiece on which the thread is to be rolled. Thereafter, the dies are synchronously rotated through one complete revolution to roll a thread on the workpiece.
This arrangement suffers certain drawbacks. First, the mechanism that displaces the dies is generally of limited stroke, and is not readily adaptable for use with a wide range of differently-sized workpieces. Second, because the dies are connected through a gear train and are not able to adjust with respect to their specific points of engagement with the workpiece, the thread dies can often bind and produce undesirable deformities in the thread form being rolled on the workpiece. Third, the rate at which the threads are formed, or the material displacement rate, is fixed by the roll geometry. Since it is not adjustable by the machine operator, this can lead to poor thread quality. Fourth, the die geometry often required specialized manufacturing techniques, and can be cost-prohibitive.
It is also known to provide other types of thread-rolling heads and attachments as well. These are representatively shown and described in U.S. Pat. Nos. 5,784,912, 4,336,703, 5,379,623, 5,568,743 and 5,924,317. The aggregate disclosures of these prior art references are hereby incorporated by reference insofar as the structure and operation of prior art thread-rolling machines and mechanisms are concerned.
Accordingly, it would be generally desirable to provide an improved thread-rolling attachment that is relatively compact, and that affords the capability of a greater range of die travel in a radial direction than available heretofore. This greater range might allow the dies to be moved sufficiently apart to offer the capability of over-the-shoulder thread-rolling. Such a shoulder is typically formed by an annular vertical surface surrounding a relatively narrow cylindrical portion of a rod-like member. For example, a valve spool might have a relatively-narrow shaft, and a radially-enlarged lobe thereon. The lobe would have annular vertical surfaces on either side of the lobe. An over-the-shoulder thread-rolling operation would entail moving the dies far apart, axially moving the dies past the lobe, and thereafter moving the dies radially inwardly to roll a thread on the workpiece on the far side of the lobe. Of course, this particular illustration is only one example of such over-the-shoulder operation.
It would also be desirable to provide an improved thread-rolling attachment that could be used on either a screw machine or on a rotary transfer machine.
With parenthetical reference to the corresponding parts, portions or surfaces of the disclosed embodiment, merely for purposes of illustration and not by way of limitation, the present invention broadly provides an improved device (30) for imparting an action to a workpiece (W). The improved device broadly includes: a slide base (31) having an axis (y-y), at least two members (32, 32) mounted on the slide base for sliding movement in a radial direction toward and away from the slide base axis; a tool, such as a thread die (33, 33), on each member; and infeed mechanism (34) for selectively causing the members to move toward the slide base axis such that the tools will engage the workpiece; and a return mechanism (35) for biasing or causing the slide members to move away from the slide base axis.
The improved device may be mounted on a screw machine in which the workpiece is rotated relative to the stationary device, or a rotary transfer machine in which the device is rotated relative to the stationary workpiece. Conceivably, the workpiece and the device might be simultaneously rotated to produce differential relative movement therebetween, and the device might possibly be used on some other type of machine as well.
In the preferred embodiment, the tools are thread-forming dies. However, other types of tools (e.g., tools for knurling, burnishing, or performing other types of forming or cutting operations, etc.) could readily be substituted therefor.
The infeed mechanism (34) includes a shell (80) movable axially relative to the slide base, and wedges (90, 90) fixed on the shell and operatively arranged to cause radial sliding movement of the members in a direction toward the slide base axis as a function of axial movement of the shell relative to the slide base. The return mechanism may simply include a return spring acting between the two members and urging them apart.
In the preferred embodiment, a timing mechanism (93) is operatively arranged to synchronize the relative rotation of the dies, notwithstanding a large degree of relative radial movement therebetween. This timing mechanism allows one die to rotate with respect to the workpiece so as to self-adjust and closely follow the track of the other die. The timing mechanism may include a sprocket (94) mounted fast to each die, and an endless chain (95) engaging the die sprockets. This timing mechanism may further include two tensioning arms (96, 96). Each arm (96) has one end (98) pivotally mounted on the slide base, and has another end (99) biased to move toward the chain, with a freely-rotatable idler sprocket (100) mounted on the arm other end and engaging the chain.
Accordingly, the general object of the invention is to provide an improved device for imparting an action (e.g., threading, knurling, burnishing, some other forming or cutting operation, etc.) to a workpiece.
Another object is to provide an improved thread-rolling end-working attachment.
Still another object is to provide an improved thread-rolling end-working attachment, which may be used on a screw machine or on a rotary transfer machine, and which affords the capability of a high degree of die travel in a radial direction within the fixed confines of an outer envelope to accommodate a wide range of differently-sized workpieces, and to afford the capability of an over-the-shoulder thread-rolling operation.
These and other objects and advantages will become apparent from the foregoing and ongoing written specification, the drawings, and the appended claims.